CPH:DOX is now in its tenth year and has quickly established itself as one of the hippest documentary festivals on the calendar – not quite the juggernaut that is IDFA in Amsterdam but certainly a buzzing industry hub. Like many city festivals, CPH:DOX permeates Copenhagen without actually seeming to have a centre, which often makes it hard to know whether you're in the right place watching the right film. But unlike most other festivals this one does seem to have an ethos, and though all the films on display are indeed documentaries, they're far removed from the flat talking-head variety that dominated the landscape in the 70s and 80s. The buzzword these days is “hybrid”, and the films programmed this year more than blurred the edges of the genre – so much so that some of them actually seemed to stand completely outside it.

As was to be expected, not everything worked. For one thing, there were a lot of prose poems, like City World, by Brent Chesanek. Heavily narrated by a young boy, with largely static, unpopulated images of Florida, it played like an offscreen Beasts Of The Southern Wild, documenting the state's history and possible future with a stately beauty but not enough energy for me. Similarly Beasts-flavoured (perhaps because it came from the same stable, production company Court 13) was Tchoupitoulas by Bill and Turner Ross, which follows three brothers bunking off to explore New Orleans after dark. I liked the freeform structure of the film, which somewhat echoes Bert Stern and Aram Avakian's 1959 classic Jazz On A Summer's Day, but there wasn't a lot to grab hold of by the end, and like a number of films here there seemed to be sleight of hand going on in the supposedly “real” events. Compared to these two, Peter Mettler's The End Of Time was positively hardcore, dealing with the issue of time in a largely abstract way that never really gets to grips with its subject but offers some stunning imagery along the way. A definite trip for scientific stoners.

Autobiography also made its mark, albeit in films that weren't ostensibly about the filmmakers. The weakest of these entries was Otto, in which Cao Guimaraes paid tribute to his partner and unborn child. This might be a nice home movie for little Otto down the line, but it felt more than a little self-indulgent to me, which is perhaps why I didn't bristle too much at the bold comparisons to Terrence Malick that preceded it. Similarly, I didn't care much for Everyone Is Older Than I Am, in which Martin Widerberg, the son of famous Swedish director Bo, sets out to finish the unfinished film that his father set out to make about his own father. That makes it sound much more Chinese box-like than it really is, because although it has a lot of heart and a very pleasant melancholic Scandi humour, there isn't too much here to set foreign territories on fire.

Into the same category we can also make room for two very tenuous additions. The first is The Lebanese Rocket Society by Joana Hadjithomas and Khalil Joreige, autobiographical only in a very general sense, telling the story of Beirut's long-forgotten space programme, which, back in the early 60s, was further advanced that Israel's. One of the more conventional docs here, this quirky and often fascinating film doesn't quite ever, ahem, blast off, but the filmmakers' excitement and sometimes wide-eyed sense of discovery is infectious. Much weirder is The Last Time I Saw Macao by João Pedro Rodrigues and João Rui Guerra da Mata, which should be hunted down by admirers of Miguel Gomes’ Tabu. This is a similarly high-end exploration of the filmmakers’ Portuguese roots, looking into the country's history through highly cinematic devices such as very specific film references (for starters, a transvestite singing the same song that Jane Russell sang in Josef Von Sternberg's 1952 underworld drama Macau is a doozy) and a very obscure film-within-a-film format that doesn't quite work in the way you think it might, since its events go largely unseen. I can't say I loved it but I went with it, and sometimes at a festival that's good enough.

But for me the standout of the autobiographical films was Max Kestner's Identitetstyveriet (pictured), or I Am Fiction, a really fantastic headspinner that rivals only Exit Through The Gift Shop as a down-the-rabbit-hole modern fable, one that feels perfectly true and yet perfectly fake – both at the same time. At its heart, it concerns a Danish chap named Thomas Skade-Rasmussen Strøbech, who, under a variety of other names, enjoyed (or does he still enjoy?) a brief but successful career as a performance artist. During this time, Strøbech teamed up with the cadaverous Claus Beck-Nielsen, with whom he formed a close, heavily stylised Gilbert and George-like alliance, doing provocative art pieces such as taking a box of democracy to Iraq – then pulling the same stunt at the White House in Washington, USA. Beck-Neilsen subsequently “killed” himself, burying an effigy of himself in a funeral that was attended by half of Copenhagen (including the Prince Of Denmark), and under his new identity Das Beckwerk published a roman a clef novel called The Sovereign in 2008.

Which is where the story starts, as Strøbech discovers that not only has Beck-Nielsen used his name for the book's main character, he has also used extensive biographical detail, some of it researched without Strøbech's knowledge. Unusually for Denmark, where court cases are rare between enemies let alone friends, Strøbech decides to sue, claiming that Beck-Nielsen has stolen his identity, even comparing him to “a vampire”. So far, so strange, but what's so compelling about the film is that it works on two levels. If it is a put-on, it perfectly articulates the relationship between author and fiction, with Strøbech as a real-life Josef K sprung to life from Kafka's pages or, much more pretentiously (on my part), Dostoyevsky's Underground Man. This is the meat of the film, with Strøbech acting out against the artist who hijacked his life and rendered him lifeless – Strøbech may be needy, boozy and often quite annoying in his quest to bring down Beck-Nielsen, but Kestner's film never loses sight of what's metaphysically fascinating about Strøbech's complaint.

At the same time, the film is really quite unexpectedly poignant. Is Strøbech losing his marbles? Or, more pertinently, is this secretly part of his ongoing artistic collaboration with Beck-Nielsen, whose angular presence is felt throughout the film, a man as shadowy and untenable as his emails are endless and verbose? It's an interesting point, and at a brisk 80-odd minutes, I Am Fiction manages to keep all these juggling balls (just about) up in the air, and though it – to put it mildly – has a very, very ragged aesthetic, it does so with the unvarnished immediacy of a newly unearthed Dogme project. As hybrids go, it was one of the more effective on offer, almost literally in a world of its own.